1. Field of the Invention
The present invention relates generally to a method and apparatus for soil treatment, and in particular to a thermal soil treatment method and apparatus.
2. Description of the Related Art
Soil contamination presents problems more and more often as industrial and business facilities age, as environmental laws requiring clean-up are toughened, and as alternate use of contaminated areas is desired. Common sites requiring soil clean up are locations of former or existing gasoline stations where the underground storage tanks for the gasoline have leaked into the soil. State and federal environmental protection agencies have become involved in clean up efforts, often setting standards to be meet in the clean up operation.
A common approach to treating soil contamination requires large scale removal of the contaminated soil from a site, transport to a treatment facility or disposal site usually using trucks to haul the soil for substantial distances over the roads, treatment of the soil in large scale ovens at the treatment facility or disposal at a secure landfill, and return of the treated soil or transportation of other soil to the original site as fill for the excavation. The removal transportation and return transportation of the soil adds considerable expense to soil clean up projects. However, the stationary large scale ovens required heretofore for effective soil decontamination requires such transport.
An object of the present invention is to avoid transport of contaminated soil by providing soil decontamination on site.
Another object of the invention is to provide a portable soil decontamination unit.
A further object of the invention is to provide a device which can be retrofit onto existing equipment to provide soil decontamination.
These and other objects and advantages of the invention are provided by an apparatus for thermal soil treatment having a soil intake, a pug mill for transporting the soil through the device while turning and mixing the soil, and a plurality of burners directed toward the soil as it is moved through the device.
In a preferred embodiment, the pug mill is provided with a roof in which the burners are mounted. In one embodiment, the burners are in opposite sides of the roof alternately spaced from one another, i.e. staggered. The burners are directed toward the center wall of the pug mill so that the staggered burners provided coverage over a wide area of the soil surface as it moves through the pug mill. The burners cause contaminants in the soil to be burned away, or at least to change to a less hazardous form, so that the soil can be returned to the site.
Since the decontamination apparatus of the present invention is portable, it is preferred that the decontamination unit be moved to the site of the contaminated soil, that the soil be placed in the decontamination unit, and that the decontaminated soil be returned to the ground at the site, all without transporting the soil for any appreciable distance.